Hydraulic control apparatus and systems



July 21, 1964 R. F. LOU'GHRIDGE 3,141,386

HYDRAULIC CONTROL APPARATUS AND SYSTEMS Filed Jan. 15, 1962 2 Sheets-Sheet 1 I23 Fl 6 I ,29

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HYDRAULIC CONTROL APPARATUS AND SYSTEMS Filed Jan. 15, 1962 2 Sheets-Sheet 2 OPEN I CLOSED OPEN H CLOSED PUMP MOTOR L OFF l l J t-! -2 1-3 FLOOR A G 5 FLOOR-D OPEN- CLOSED l OPEN SV-I j CLOSED PUMP MOTOR OFF l I l J t-4 t-5 t-6 1-7 FLOOR B G 6 FLOOR A CAR CONTROLLER PUMP MOTOR SV-I SV-2 SV-3 SV-4 CONTROLLER (N. C.) (N.C.) (N.C.) (N.O.)

CAM SELECTOR CONTROLLER INVENTOR. 7 ROBERT F. LOUGHRIDGE BY ATTORNEY United States Patent 3,141,386 HYDRAULKC CQNTROL APPARATUES AND SYSTEMS Robert F. Loughridge, 2343 Winter: Terrace W., Fort Worth, Tex. Filed Jan. 15, 1962, Ser. No. 166,192 6 Gaines. (Cl. 91-4161) My invention relates generally to hydraulic control apparatus and systems, and more particularly to hydraulic control valves and valve arrangements which are adapted for control purposes in a fluid actuated system.

The hydraulic control valves and valve arrangements of the present invention may be useful in various applications; however, they are especially applicable to hydraulic elevator systems. It is of course desirable that a hydraulic elevator should accelerate smoothly and rapidly to operating speed when leaving a floor and decelerated smoothly and rapidly when approaching a floor. It should also, accurately level itself at each floor and do all of these things effectively with varying elevator loads. Also, it is essential that the hydraulic system should incorporate adequate safety features. The hydraulic control valves and valve arrangements of the prior art, of which I am aware, have not proved to be entirely satisfactory for adequate accomplishment of the objectives above-mentioned.

It is accordingly an object of the present invention to provide hydraulic control valves and arrangements which shall be capable of accomplishing the objectives abovementioned.

Another object of the present invention is to provide improved hydraulic control valves and arrangements to accomplish effective control of a hydraulic elevator for all elevator load conditions.

Another object of the present invention is to provide an improved hydraulic control valve, the action of which is modified in accordance with hydraulic system pressure.

Another object of the present invention is to provide an improved hydraulic control valve which will automatically seek and maintain a preselected open position.

Another object of the present invention is to provide improved hydraulic control valves which are capable of properly assuming an operating position in addition to the open and close positions.

These and other objects are effected by my invention as will be apparent from the following description taken in accordance with the accompanying drawings, forming a part of this application, in which:

FIG. 1 is a schematic longitudinal sectional view of a first control valve in accordance with a preferred embodiment of the invention;

FIG. 2 is a schematic longitudinal section of a second control valve in accordance with a preferred embodiment of the invention;

FIG. 3 is a schematic diagram of the fluid system of a hydraulic elevator in accordance with a preferred embodiment of the invention;

PEG. 4 is a sectional view taken along the line 44 of FIG. 1;

FIGS. 5 and 6 are graphs to aid in explanation of the operation of the hydraulic fluid system of FIG. 3; and,

FIG. 7 is a schematic diagram of electrical controls pertaining to the system of FIG. 3.

Referring now to the drawings, FIG. 1 shows a first, or up-control valve 11 constructed in accordance with the present invention, which includes a valve body 13 having a threaded inlet aperture 15 for the entry of fluids generally in the direction of the flow-arrow A, and a threaded outlet aperture 17. Internally, the valve is fitted with a valve seat 19 supported by structure 21 integrally attached to the valve body 13 and a valve aperture 23 through ICC which fluids may flow. The valve body 13 has a main valve cavity 25, a mid-body cavity 27 and a lower-body cavity 2% and a threadedly connected valve cap 31. An O-"ing 33 provides an eflective seal between the valve body cap 31 and the valve body 13.

Within the mid-body cavity 27 there is a valve disc 35 having a frusto-conical portion 37 which abuts against the valve seat 19 and prevents the flow of fluid through the valve. Extending above the top of the valve disc 35, there is a tubular valve skirt 39 which is slidable within the valve apertures 23. Below the frusto-conical portion 37, the valve disc 35 is generally cylindrical and is slidable in the mid-body portion 41, except that there are a lurality of flat areas 43 (See FIG. 4) parallel to the longitudinal axis of the valve disc 35. The valve disc 35 is integrally connected by a cylinder 45 to a piston 47, preferably of circular shape and larger in diameter than the valve disc 35. The piston 47 is slidable in the lowerbody cavity 29 and has a groove 49 in its periphery which is adaptable to receive a sealing device 51 to prevent the flow of fluids thereby.

Centered in the valve cap 31 is a threaded aperture 53 into which an adjustable threaded sleeve 55 is inserted. The threaded sleeve has central cavity 57 and a top end closure 59 which has a central aperture 61. A lock nut 63 encircles the threaded sleeve 55 and holds it in fixed relation to the piston 51. A cap es is threadedly connected to the open bottom end of the threaded sleeve 55 and, together with a gasket 67, seals the cavity 57.

An elongated pin 69, which is slidable in a central aperture 71 extending through the valve disc 35, the cylinder 45 and the piston 51, terminates at its lower end in a head portion 73 operable in the cavity 57, and at its upper end in the main valve cavity 25. A compression spring 75 encircles the pin 69 at its lower end region and is disposed within the threaded sleeve central cavity 57. The pin 69 is tubular, having a central longitudinal cavity 77 which communicates at its upper end with the main valve cavity 25. There is an orifice 79 through the tubular wall near the bottom of the cavity 77 affording communication from the lower-body cavity 29 with the central longitudinal cavity 77.

A series of connected passages 31 affords communication between the lower-body cavity 29 and a threaded terminal 83 integrally attached to the valve body 13.

Referring again to the drawings, FIG. 2 illustrates a second, or down-control valve 85, constructed in accordance with the present invention, which includes a valve body 87 having a threaded inlet aperture 89 for the entry of fluids generally in the direction of the flow arrow B, and a threaded outlet aperture 91. Internally, the valve is fitted with a valve seat 93 supported by structure 95 integrally attached to the valve body 87, and a valve aperture 97 through which fluids may flow. The valve body 87 has a main valve cavity 99, a mid-body cavity 101 and an upper-body cavity 1693 and a threadedly connected valve body cap 105. An O-ring gasket 107 effectively seals the joint between the valve body 87 and the body cap 105.

Within the mid-body cavity 161 there is a valve disc 109 which is similar to the valve disc 35 of FIG. 1. The valve disc M9 is integrally connected by a cylinder 111 to a piston 113, preferably of circular shape and larger in diameter than the valve disc 1139. The piston 113 is slidable in the upper-body cavity 163 and has a groove 115 in its periphery which is adaptable to receive a sealing device 117 to prevent the flow of fluids thereby.

Centered in the valve body cap is an adjustable elongated spindle 119, the upper portion of which is threaded into the valve body cap 1il5, while the lower portion is cylindrical and is slidable in a central cavity 121 both in the piston 113 and in the cylinder 111. The

spindle 119 has a central longitudinal cavity 123 extending for approximately three-quarters of its length from the top end, and there is an orifice 125 in the tubular wall near the bottom of the cavity 123 which aflords communication with the upper-body cavity 103 and the central cavity 123. A lock nut 127 encircles the adjustable spindle 119 and holds it in fixed relation to the piston 113.

An adjustable stop bolt 129 and lock nut 131 is inserted through the valve body cap 105 a suflicient distance to limit the upward movement of the piston 113 when the valve opens. (FIG. 2 illustrates the valve 85 in the closed position.) The valve body cap is fitted, also, with a passage 133 and threaded cavity 135 which aflords communication between the upper-body cavity 193 and a threadedly connected conduit means (not shown).

A series of connected passages 137 aflord communication between the mid-body cavity 1131 and the upperbody cavity 103. An adjustable needle valve 139 is provided in a convenient location to regulate the flow of fluid through the passages 137.

The lower periphery of the valve body 37 is fitted with an axially threaded boss 141 into which an adjustable rotatable stem 143 is threaded. The lower extremity of the stem 143 is provided with a rotating means, preferably a handwheel 145, secured to the stem 143 by a nut 147.

Now in order to describe the manner in which the up-control valve 11 and the down-control valve 85 are used, reference is made to FIG. 3. A modern hydraulic elevator system (see FIG. 3) includes a fluid reservoir 149, preferably located in an elevated position with respect to a fluid pump 151 which is operated by an electric motor (not shown). A fluid line 153 of suitable size connects the reservoir and the inlet of the pump 151. The discharge side of the pump is connected to a main fluid line 155 of suitable size which leads directly to an elevator jack 157 through a check valve 159 and a muffler 161. The main fluid line 155 has a branch line 163 for the purpose of conducting fluid to the up-control valve 11 and another branch line 165 for the purpose of conducting fluid to a needle valve N-3 in series with a solenoid valve SV-3, and a needle valve N- in parallel therewith. Fluid flows through these valves to the upcontrol valve 11 in accordance with a predetermined sequence of operations. Fluid leaves the up-control valve either vie fluid line 167 through a solenoid valve SV-4 or via fluid line 169 to the reservoir 149. A third branch line 171 conveys fluid from the main line 155 to the down-control valve 35 in accordance with a predetermined sequence of operations, and thence, via fluid line 173, through the solenoid valve SV-1 and the needle valve N-1 to the reservoir 149. Also, fluid may flow via the fluid line 175 and the solenoid valve SV2 and the needle valve N-2 to the reservoir 149. Likewise, the fluid may flow through the down-control valve 35 and via fluid line 177 to the reservoir 149.

To understand the manner in which the up-control and the down-control valves 11, 85 and the leveling system operate, it will be helpful to consider the sequence of operations required to move an elevator car 179, initially at rest, from Floor A to Floor B at some higher elevation, and then to lower the car from Floor B to Floor A. For the purpose of explanation, it will be assumed that the car 179 has a nominal load imposed thereon which is within its rated capacity, but this should not be understood as a limitation, since the sequence of operations and the valves perform in the same manner for all car loads.

With the car at Floor A and at rest, the following conditions prevail: The system is full of hydraulic fluid and the reservoir is filled to its normal operating level; the pump is not in operation and no fluid is flowing in the system; the down-control valve 85 is closed and the load on the car 179 and the jack 157 is held by the check valve 159 which is closed. Further, the up-control valve 4 11 is open; the solenoid valve SV-3 is closed; the solenoid valve SV-4 is open.

To start upward, the up-button (not shown, but a part of the car controller generally indicated as a block 183 in FIG. 7) is pushed at time t-1 in FIG. 5 whereupon, the solenoid valve SV-3 opens; the solenoid valve SV-4 closes; the pump motor starts and operates the pump 151 which causes fluid to flow to the up-control valve 11 via line 163 and line 165. Most of the fluid flowing to the up-control valve 11 via line flows through N-3 and SV-3, while the remainder, which is a smaller quantity, flows through N-5. The fluid entering the up-control valve 11 via line 163 flows past the valve disc 35 through a plurality of apertures 181 (see FIG. 4) into the midbody cavity 27 (see FIG. 1). Also, fluid flows through the up-control valve 11 in the direction of the flow arrow in the normal manner, and flows via line 169 to the reservoir 149. Likewise, the fluid entering the up-control valve 11 via line 165 flows through the passages 81 into the lower-body cavity 29 below the piston 47. Furthermore, the fluid flows through the aperture 61, around the head portion 73 and into the central cavity 57.

The fluid acting on the lower side of the piston 47 and the lower side of the valve disc 35 produces a force upward. Similarly, the fluid acting on the upper side of the piston 47 and the valve disc 35 produces a force downward. But, since the lower piston area plus the valve area is greater than the upper piston and valve area, the resultant force is directed upwards. Therefore, the up-control valve will start to close.

As the up-control valve 11 starts to close, more fluid flows through line 155 to the jack 157 with the result that the elevator car moves upward toward Floor B.

During the movement upward of the piston 47, the orifice 79 is uncovered and fluid may escape through it and the central cavity 77 to the main valve cavity 25. The fluid flows thence via the line 169 to the reservoir 149. However, the relative loss of fluid via the orifice 79 is small compared with the flow of fluid into the lowerbody cavity 29, so that this loss has little or no appreciable eflect and the up-control valve 11 closes.

When the up-control valve 11 is fully closed, the pump 151 delivers full rated output to the jack 157 via line 155, and the car 179 moves upward at its rated speed. Now, as the car approaches Floor B, at time t-2 (see FIG. 5), a cam (not shown, but a part of the cam selector generally indicated as a block 185 in FIG. 7), actuates a switch which closes an electric circuit and causes the solenoid valve SV-3 to close. This stops most of the flow of fluid to the lower-body cavity 29 via passages 81, with the result that the fluid lost via the orifice 79 is not replenished and the predominance of force, mentioned hereinbefore, acting upwardly is lost. Thus, the piston 47 moves downwardly. As the piston 47 moves down, the up-control valve 11 opens partially, allowing some of the fluid to flow via lines 163, 169 to the reservoir 149. Consequently, the fluid flowing to the jack 157 is lessened and the upward speed of the car 179 is slower. The upcontrol valve 11 will continue to open until the piston 47 covers the orifice 79, at which time the fluid loss through the orifice 79 ceases.

That the fluid can no longer escape from the lowerbody cavity 29 via the orifice 79 recreates, immediately, the differential upward force. The piston 47 will not continue to move downward, but will remain in a position covering or nearly covering the orifice 79. Consequently, the location of the orifice 79 is important, as it determines the proportionate valve opening and therefore the leveling speed. The location of the orifice 79 is adjustable with respect to the piston 47 so that any desired leveling speed may be established. The threaded sleeve 55 may be positioned for the most desirable leveling speed when there is no load on the car 179; and then, by means of the lock nut 63, it may be fixed in that position. Thereafter, fluid at line pressure acts on the head portion 73 forcing it against the spring 75. As it does so, the orifice 79 will automatically locate at an equilibrium position for any load on the elevator and pressure in the system.

When the car reaches the level of Floor B, at time t-3 (see FIG. 5), cams on the cam selector controller 185 actuate switches which open electric circuits, de-energizing the solenoid valve SV-4 so that it opens and also stopping the pump motor. The opening of SV-4 allows all the fluid in the lower-body cavity to flow via the passages 81 and line 167 back to the reservoir 149. The piston 47 falls rapidly by both gravity and the pressure of the fluid on the upper surface areas, and so there is no longer any fluid entering the jack 157. Thus, the car stops at Floor B and is held there by the fluid acting against the closed check valve 159.

In order to describe the operating of the valves 11, 85 and the system when lowering the car 179 from Floor B to Floor A, reference is now made to FIGS. 3 and 6.

The following conditions prevail with the car 179 at rest at Floor B. The pump 151 is not operating; the check valve 159 is closed and is holding the car 179 and its load, if any, at Floor B; the up-control valve 11 is open; the solenoid valves SV-S, SV-4 are closed and open respectively; the down-control valve 85 is closed and both the solenoid valves SV-1, SV-Z are closed.

The purpose of the down-control valve 35 may be understood more completely by observing that, while closed, the fluid in the system entering the valve in the direction of the flow arrow B, flows past the flat sides of the valve disc (similar to aperture 181 shown in FIG. 4) and fills the mid-body cavity 191 below the piston 113. Fluid passing the needle valve 139 enters the passages 137 and fills the upper-body cavity 103. Fluid in this cavity has two possible routes of flow: via the outlet 133 which communicates via line 173 with the solenoid valve SV-1, or via the orifice 125 which communicates via the central cavity 123 and line 175 with the solenoid valve SV2. Since the area of the upper side of the piston 113 plus the area of the upper side of the valve disc 109 is greater than the area of the underside of the piston 113, the down-control valve 85 remains closed.

To start downward, the down-button (on car controller 183) is pushed at time t4 (see FIG. 6), whereupon solenoid valve SV-1 opens while soleniod valve SV2 remains closed. Fluid in the upper-body cavity 103 flows via line 173 through the solenoid valve SV1 to the reservoir 149. Since the differential pressure holding the down-control valve 85 closed no longer exists, the downcontrol valve begins to open. Fluid can flow from the jack through the partially open down-control valve 35, and this causes the elevator car 179 to begin to move downward. As fluid flows through the down-control valve 85 and via line 177 back to the reservoir 149, the down-control valve 85 continues to open until the piston 113 strikes the adjustable stop bolt 129. In this position, the piston 113 covers orifice 125 and no fluid flows through it.

As the elevator car approaches Floor A, at t-S, a cam on the cam selector controller 185, actuates a switch which closes an electric circuit energizing the solenoid valve SV2, which opens.

While the car 179 continues to descend and approach Floor A, at t-6 another cam on the cam selector controller 1S5, actuates a switch which de-energizes solenoid valve SV-1 which closes. Fluid, nevertheless, continues to flow into the upper-body cavity 193 and, since there is no open passage by which it can escape, the fluid pressure builds up on the upper surface of the piston 113. Immediately, the pressure builds up and the piston moves downward toward the closed position. However, when the orifice 125 is uncovered again, fluid flows through it at a rate equal to the flow past the needle-valve 139 and, through the passages 137 into the cavity. Fluid now flows 6 via the line and the solenoid valve SV-Z into line 177 and back to the reservoir 149. At this moment, the downward movement of the piston 113 ceases; the downcontrol valve 85 is closed partially, and the car descends toward Floor A at a uniform leveling speed, which is some proportionate part of the open-valve speed.

At the moment the car reaches the level of Floor A, at time t7 of FIG. 6, another cam on the cam selector controller actuates a switch which opens a circuit causing the solenoid valve SV2 to close. The closing of the valve SV-2 produces immediately a build-up of differential pressure downward on the piston 113 and the down-control valve 85 closes. In this situation all of the fluid in the jack 157 is held by the check valve 159 and the car 179 remains at Floor A.

It will be evident to those skilled in the art that, in the embodiments thus illustrated and described, the invention is characterized by hydraulic control valves 11, 85 and an arrangement of these valves in a control system which is especially applicable to hydraulic elevators. The functions and operations of separate control devices in the prior art, are effectively combined in my up-control valve 11. Likewise, my down-control valve 85 combines in a single valve the functions and operations of other control devices which were heretofore separate. By incorporating these valves in my improved control system, effective operation of the elevator car is enhanced, and is independent of the load on the car 179.

It is most desirable that a hydraulic elevator accelerate smoothly and rapidly upward and that it decelerate smoothly and rapidly when approaching a floor. It should, also, descend in a smooth manner and decelerate smoothly and rapidly as it approaches a floor. It is evident that the valves and the system of the present invention accomplish this purpose most effectively. In my system the entire output of the pump 151 initially flows through the up-control valve 11. Then as the valve 11 automatically closes, the car 179 is brought to full upward speed. Later, when a signal is given (at t2) the valve 11 opens partially, in the manner explained herein before, and the car automatically assumes a proper leveling speed. The upcontrol valve 11 automatically adjusts to the load on the car 179. The fluid pressure in the system is dependent on the load on the car. Therefore, the fluid acts on the head portion 73 and causes it to move upwards against the spring 75 to an equilibrium position. This equilibrium position determines also, the location of the orifice 79 relative to the piston 4-7 and accordingly, the amount the valve 11 will open. It is clear, therefore, that once the orifice 79 is properly located for a given load condition, for example no load, a change in load will automatically produce a change in the location of the orifice 79. This controls the amount the valve 11 opens and the leveling speed of the car 179.

It is important to observe that the solenoid operated valve SV-4 is a dual-function valve. Firstly, it serves in the capacity described hereinbefore; secondly, it serves as a safety measure in the following manner: the elevator car 179 while moving upward, cannot over-travel the selected floor because at floor level a cam on the cam selector control 185 actuates a switch which causes the valve SV-4 to open. Immediately, the fluid in the lower body cavity 29 flows via the passages 81, through the valve SV4 and fluid line 167 back to the reservoir 149. Simultaneously, the pressure on the upper surface of the piston 47 causes it to move downward, thus, opening fully the up-control valve 11. It should be clear that the full opening of the up-control valve 11, under the premise above, results in the stopping of the elevator car 179 at floor level.

If for any reason the system becomes inoperative and it is not possible to lower the car 179 to ground level in the normal manner, it is always possible to open the down-control valve 85 manually and allow the fluid to flow from the jack 157 via the valve 85 back to the reservoir 149. This may be accomplished by rotating the handwheel 145, which causes the upper end of the stem 143 to bear against the valve disc 109 until it lifts the valve disc 109 from the valve seat 93. This will allow fluid to flow through the valve under manual control when emergencies arise.

It should be obvious to those skilled in the art, that the needel valve 139 may be adjusted to control the rate of flow of fluid to the upper body cavity 1%, and that by adjusting both needle valves N-l and NZ relative thereto, a safe and comfortable rate of descent and down leveling of the car may be accomplished.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

I claim:

1. A hydraulic control valve comprising: a valve body having fluid inlet and outlet apertures and adjustable means therein to control the flow of fluid through said valve body; a piston slidable in said valve body; means connecting said piston and said flow control means; an aperture through said piston and said flow control means; a first fluid cavity in said valve body between said piston and said flow control means; a first fluid communicating passage between said inlet aperture and said first fluid cavity; a cap attached to said valve body; a second fluid cavity in said valve body between said piston and said cap; a second fluid communicating passage connecting said second fluid cavity and the exterior of said valve body; an adjustable sleeve disposed in said cap; a third fluid cavity within said sleeve formed by an end closure on the outward end thereof and an opposite end closure having a central aperture therein; an elongated fluid actuated pin having a reciprocable head in said third fluid cavity and a shank extending through said end closure central aperture and said aperture in said piston and flow control means; spring bias means within said third fluid cavity abutting said head and said opposite end closure; a central longitudinal fluid cavity in said shank; and a third fluid communicating passage between said second fluid cavity and said shank cavity.

2. A hydraulic control valve comprising: a valve body having inlet and outlet apertures, and a main passage communicating between said apertures; a valve closure including a movable element interposed in said main passage; a cylinder, and a piston reciprocable in said cylinder; a first fluid cavity formed by said piston and cylinder on one side of said piston, and a second fluid cavity formed by said piston and cylinder on the other side of said piston; means linking said movable element to said piston for movement therewith; first fluid passage means communicating between said inlet aperture and said first cavity; second fluid passage means communicating between said second cavity and the exterior of said cylinder; an aperture in said piston and extending in the direction of piston movement; a pin slidably received by said piston aperture; a third cavity within said pin and extending longitudinally thereof, and an orifice communicating between said third cavity and the pin exterior, said orifice being positioned such that it is exposed to said second cavity when said valve is closed and blocked by said piston when said valve is partially opened; third fluid passage means communicating between said third cavity and said outlet aperture; resilient bias means opposing movement of said pin in the axial direction toward said first cavity from said second cavity; and means allowing pressure of fluid in said second cavity to act on said pin in a direction to oppose the force of said bias means.

3. A hydraulic control valve comprising: a valve body having inlet and outlet apertures, and a main passage communicating between said apertures; a valve closure including a movable element interposed in saidmain passage; a cylinder, and a piston reciprocable in said cylinder; a first fluid cavity formed by said piston and cylinder on one side of said piston, and a second fluid cavity formed by said piston and cylinder on the other side of said piston; means linking said movable element to said piston for movement therewith; first fluid passage means communicating between said inlet aperture and said first cavity; second fluid passage means communicating between said second cavity and the exterior of said cylinder; an aperture in said piston and extending in the direction of piston movement; a pin slidably received by said piston aperture; a third cavity Within said pin and extending longitudinally thereof, and an orifice communicating between said third cavity and the pin exterior, said orifice being positioned such that it is exposed to said second cavity when said valve is closed and blocked by said piston when said valve is partially opened; third fluid passage means communicating between said third cavity and said outlet aperture; resilient bias means opposing movement of said pin in the axial direction toward said first cavity from said second cavity; means allowing pressure of fluid in said second cavity to act on said pin in a direction to oppose the force of said bias means; and calibrating means for adjusting the position of said orifice relative to said piston.

4. In a hydraulic elevator system including a car; a jack having a fluid inlet; a fluid reservoir having a fluid outlet and a fiuid inlet; a fluid pump having a fluid outlet and a fluid inlet; a check valve having a fluid outlet and a fluid inlet; a hydraulic control valve comprising: a valve body having inlet and outlet apertures, and a main passage communicating between said apertures; a valve closure including a movable element interposed in said main passage; a cylinder, and a piston reciprocable in said cylinder; a first fluid cavity formed by said piston and cylinder on one side of said piston, and a second fluid cavity formed by said piston and cylinder on the other side of said piston; means linking said movable element to said piston for movement therewith; first fluid passage means communicating between said inlet aperture and said first cavity; second fluid passage means communicating between said second cavity and the exterior of said cylinder; an aperture in said piston and extending in the direction of piston movement; a pin slidably received by said piston aperture; a third cavity within said pin and extending longitudinally thereof, and an orifice communicating between said third cavity and the pin exterior, said orifice being positioned such that it is exposed to said second cavity when said valve is closed and blocked by said piston when said valve is partially opened; third fluid passage means communicating between said third cavity and said outlet aperture; resilient bias means opposing movement of said pin in the axial direction toward said first cavity from said second cavity; and means allowing pressure of fluid in said second cavity to act on said pin in a direction to oppose the force of said bias means; fluid conduit means connecting said reservoir outlet to said pump inlet; fluid conduit means connecting said pump outlet to said check valve inlet; fluid conduit means connecting said check valve outlet to said jack inlet; conduit means connecting said pump outlet to said control valve inlet aperture; conduit means connecting said control valve outlet aperture to said reservoir inlet; a first normally closed solenoid valve having an inlet and an outlet; conduit means connecting said pump outlet to said solenoid valve inlet; conduit means connecting said solenoid valve outlet to said control valve second fluid passage means; a second normally open solenoid valve having an inlet and an outlet; conduit means connecting the outlet of said normally open solenoid valve to said reservoir inlet; conduit means connecting said control valve second fluid passage means to the inlet of said normally open solenoid valve; means for opening said first solenoid valve and closing said second solenoid valve preparatory to movement of said car in the upward direction; means for closing said first solenoid valve as said car nears a floor terminal; and means for closing said second solenoid valve When said car arrives at said floor terminal. 5

5. The invention as set forth in claim 4, including needle valve means for controlling fluid flow through said first solenoid valve.

6. The invention as set forth in claim 5, including calibrating means for adjusting the position of said con- 10 trol valve pin orifice relative to said control valve piston.

References Cited in the file of this patent UNITED STATES PATENTS Everstam Nov. 10, 1925 Prosser Sept. 17, 1940 Joseph May 15, 1951 Mapes Aug. 19, 1952 Arbogast et a1. Sept. 27, 1960 FOREIGN PATENTS Great Britain Oct. 29, 1958 

4. IN A HYDRAULIC ELEVATOR SYSTEM INCLUDING A CAR; A JACK HAVING A FLUID INLET; A FLUID RESERVOIR HAVING A FLUID OUTLET AND A FLUID INLET; A FLUID PUMP HAVING A FLUID OUTLET AND A FLUID INLET; A CHECK VALVE HAVING A FLUID OUTLET AND A FLUID INLET; A HYDRAULIC CONTROL VALVE COMPRISING: A VALVE BODY HAVING INLET AND OUTLET APERTURES, AND A MAIN PASSAGE COMMUNICATING BETWEEN SAID APERTURES; A VALVE CLOSURE INCLUDING A MOVABLE ELEMENT INTERPOSED IN SAID MAIN PASSAGE; A CYLINDER, AND A PISTON RECIPROCABLE IN SAID CYLINDER; A FIRST FLUID CAVITY FORMED BY SAID PISTON AND CYLINDER ON ONE SIDE OF SAID PISTON, AND A SECOND FLUID CAVITY FORMED BY SAID PISTON AND CYLINDER ON THE OTHER SIDE OF SAID PISTON; MEANS LINKING SAID MOVABLE ELEMENT TO SAID PISTON FOR MOVEMENT THEREWITH; FIRST FLUID PASSAGE MEANS COMMUNICATING BETWEEN SAID INLET APERTURE AND SAID FIRST CAVITY; SECOND FLUID PASSAGE MEANS COMMUNICATING BETWEEN SAID SECOND CAVITY AND THE EXTERIOR OF SAID CYLINDER; AN APERTURE IN SAID PISTON AND EXTENDING IN THE DIRECTION OF PISTON MOVEMENT; A PIN SLIDABLY RECEIVED BY SAID PISTON APERTURE; A THIRD CAVITY WITHIN SAID PIN AND EXTENDING LONGITUDINALLY THEREOF, AND AN ORIFICE COMMUNICATING BETWEEN SAID THIRD CAVITY AND THE PIN EXTERIOR, SAID ORIFICE BEING POSITIONED SUCH THAT IT IS EXPOSED TO SAID SECOND CAVITY WHEN SAID VALVE IS CLOSED AND BLOCKED BY SAID PISTON WHEN SAID VALVE IS PARTIALLY OPENED; THIRD FLUID PASSAGE MEANS COMMUNICATING BETWEEN SAID THIRD CAVITY AND SAID OUTLET APERTURE; RESILIENT BIAS MEANS OPPOSING MOVEMENT OF SAID PIN IN THE AXIAL DIRECTION TOWARD SAID FIRST CAVITY FROM SAID SECOND CAVITY; AND MEANS ALLOWING PRESSURE OF FLUID IN SAID SECOND CAVITY TO ACT ON SAID PIN IN A DIRECTION TO OPPOSE THE FORCE OF SAID BIAS MEANS; FLUID CONDUIT MEANS CONNECTING SAID RESERVOIR OUTLET TO SAID PUMP INLET; FLUID CONDUIT MEANS CONNECTING SAID PUMP OUTLET TO SAID CHECK VALVE INLET; FLUID CONDUIT MEANS CONNECTING SAID CHECK VALVE OUTLET TO SAID JACK INLET; CONDUIT MEANS CONNECTING SAID PUMP OUTLET TO SAID CONTROL VALVE INLET APERTURE; CONDUIT MEANS CONNECTING SAID CONTROL VALVE OUTLET APERTURE TO SAID RESERVOIR INLET; A FIRST NORMALLY CLOSED SOLENOID VALVE HAVING AN INLET AND AN OUTLET; CONDUIT MEANS CONNECTING SAID PUMP OUTLET TO SAID SOLENOID VALVE INLET; CONDUIT MEANS CONNECTING SAID SOLENOID VALVE OUTLET TO SAID CONTROL VALVE SECOND FLUID PASSAGE MEANS; A SECOND NORMALLY OPEN SOLENOID VALVE HAVING AN INLET AND AN OUTLET; CONDUIT MEANS CONNECTING THE OUTLET OF SAID NORMALLY OPEN SOLENOID VALVE TO SAID RESERVOIR INLET; CONDUIT MEANS CONNECTING SAID CONTROL VALVE SECOND FLUID PASSAGE MEANS TO THE INLET OF SAID NORMALLY OPEN SOLENOID VALVE; MEANS FOR OPENING SAID FIRST SOLENOID VALVE AND CLOSING SAID SECOND SOLENOID VALVE PREPARATORY TO MOVEMENT OF SAID CAR IN THE UPWARD DIRECTION; MEANS FOR CLOSING SAID FIRST SOLENOID VALVE AS SAID CAR NEARS A FLOOR TERMINAL; AND MEANS FOR CLOSING SAID SECOND SOLENOID VALVE WHEN SAID CAR ARRIVES AT SAID FLOOR TERMINAL. 